I. Technical Field
The present invention relates to peptides from the three type I repeats of human endothelial cell thrombospondin, and analogs and peptidomimetics based on these sequences which bind to sulfated glycoconjugates including heparin and sulfatide.
The invention also relates to conjugates of peptides from the three type I repeats of human endothelial cell thrombospondin with polysucrose or dextran.
The invention also relates to peptide mimetics and analogs based on the active thrombospondin sequences and conjugates thereof, and thiol derivatives thereof.
Additionally the invention relates to the use of the thrombospondin-derived peptides and conjugates as inhibitors of endothelial cell growth.
The invention also relates to the use of the peptides, analogs, and peptidomimetics, and conjugates derived from thrombospondin as inhibitors of tumor cell growth, including inhibition of breast cancer cell growth and melanoma cell growth.
The invention relates to the use of the peptides and conjugates of thrombospondin for treatment of Kaposi's sarcoma.
The invention relates to a method of treating a subject suffering from disease, involving abnormal vascular proliferation, including cancer, comprising administering to the subject peptides or peptide conjugates in a pharmaceutically acceptable carrier.
II. Background of the Invention
Heparin binding is critical for activities associated with many cellular growth factors, cell adhesion molecules, and certain enzymes involved in the blood clotting cascade. Agents to inhibit these interactions have found numerous uses in prevention of thrombosis. Heparin analogues have been shown to have anti-tumor and antimetastatic activities.
Peptides that bind to heparin have been identified or isolated from many heparin binding proteins (see, e.g., Cardin et al., Arteriosclerosis, Vol. 9, pages 21-32 (1989)). Examples of heparin binding peptides identified from adhesion molecules include type IV collagen, laminin, and fibronectin. All have clusters of basic amino acids which fit consensus sequences defined by comparison of many heparin binding proteins (see Cardin et al., as above). The binding constants of the Cardin et al peptides and other peptides described in this art area are in the general range of 10.sup.4 to 10.sup.3 molar.sup.-1.
Peptides from malaria circumsporozoite protein have been disclosed to mediate cell adhesion (Rich et al., Science, Vol 249:1574-1577 (1990)). Such peptides suffer from the disadvantages of not binding heparin and the adhesion activity was ascribed to a sequence Val--Thr--Cys--Gly (SEQ ID NO:5), which is inactive for heparin binding.
Peptides from thrombospondin have been disclosed (Prater et al., J. Cell Biol. Vol 112, pages 1031-1040 (1992)). The sequences of Prater have a significant disadvantage since they are insufficient to bind to heparin or related sulfated glycoconjugates with high affinity.
Accordingly, there is a need in the present art for highly potent peptides that will bind to heparin or related sulfated glycoconjugates with high affinity. There is particularly a need for such peptides which are also useful to prevent interaction of heparin or related sulfated glyconjugates with adhesion molecules, growth factors, cells or heparin-dependent enzymes. Accordingly, it is an object of the present invention to overcome the difficulties in the prior art as described above.